A photoacoustic imaging technology has been developed in recent years. This technology uses a probe or other receiving unit with a receiving element to receive an acoustic wave (photoacoustic wave) and obtains a pressure signal of the acoustic wave, the acoustic wave being generated by a photoacoustic effect when a measuring object is irradiated with light. This technology, therefore, can obtain a three-dimensional pressure distribution or optical characteristic value distribution of the inside of the measuring object. In other words, reconstruction can be realized. Therefore, when the measuring object is a living body, this technology can be applied to a medical field where the inside of the living body is imaged in order to observe a tumor.
A pressure signal measured in photoacoustic imaging deteriorates due to the influence of an impulse response of a receiving unit. This consequently reduces the resolution and contrast of a three-dimensional pressure distribution image obtained as a result of reconstruction. The influence of the impulse response of the receiving unit needs to be eliminated in order to improve the resolution and contrast. The operation for removing the influence is mathematically equivalent to convolution inverse operation, which is called “deconvolution” operation.
Non Patent Literature 1 discloses an example of a deconvolution method used in photoacoustic imaging. Non Patent Literature 1 discloses a method for actually measuring an impulse response of a receiving unit to perform deconvolution on a pressure signal. More specifically, this method concentrates excitation light into a fine region and uses a pressure signal, which is generated from the region, as an approximate value of the impulse response.